The present invention concerns an optical object detection system which detects physical objects located outside an operating vehicle.
Devices for detecting vehicles or other physical objects located ahead of or to the rear of an operating vehicle using laser radar have been proposed in the past. For example, in Japanese Patent Application Kokai No. Hei 06-150196, a method is described. Moving physical objects located ahead of the vehicle mounting the detection system are detected by laser radar. Information concerning the detected moving physical objects is stored in a memory, and control such as a tracking operation, etc., is performed. Specifically, if a moving physical object stored in the memory is not detected in the current detection process, the information concerning the moving physical object is retained in the memory as a detection error due to some cause until non-detection occurs a predetermined number of times. Then, when such a failure has occurred a predetermined number of times, the information concerning this moving physical object is deleted from the memory.
However, in such a method, if the number of times that a physical object that is not detected is retained without being deleted from the memory (i.e., the number of times of interpolation) is increased, the following problem arises. Namely, although such an increase makes it possible to continue the recognition of external physical objects in a more continuous manner, the interpolation treatment creates erroneous recognition which makes it appear as though an external physical object is present in the detection area of the system even when the external physical object has moved out of the detection area. Conversely, if the number of times of interpolation is decreased, the recognition of physical objects becomes intermittent as a result of detection error by the system.
In accordance with one aspect of the invention, an object detection system of the invention is mounted on a vehicle and comprises a physical object recognition unit which recognizes physical objects outside the vehicle, and a physical object memory which stores information concerning the physical objects. A controller recognizes presence of a physical object when the physical object is sensed by one or more sensors a predetermined number of times, which is larger for a central portion of the detecting area than for a peripheral portion of the detecting area.
The frequency of erroneous recognition due to erroneous detection is reduced compared to cases in which the recognition of physical objects is accomplished a fixed number of times regardless of the detection area. Physical objects that have entered the boundary portions of the detection area can quickly be recognized. When detecting a physical object located ahead of the vehicle inside the detection area, it is impossible for the physical object to suddenly appear in the center of the area. Conversely, at the edges of the detection area, a physical object may sometimes suddenly appear inside the detection area as seen by the sensors, as a result of a moving physical object entering the inside of the detection area from outside of the detection area. In view of such realistic conditions, the number of times of detection required for recognition is set at a large value in the center of the detection area in order to prevent erroneous recognition. On the other hand, at the edges of the detection area, since physical objects may suddenly appear as a result of the movement of moving physical objects or the behavior of the vehicle mounting the system, the number of times of detection required for physical object recognition is set at a small value.
According to another aspect of the invention, an object detection system of the invention comprises at least one sensor for sensing a physical object in a predetermined detecting area, a controller for recognizing presence of a physical object based on output from said sensor, and a memory for storing information about the physical object recognized by the controller. The controller holds the physical object stored in the memory indicating that the physical object is present until the controller fails to recognize presence of the corresponding physical object a predetermined number of recognition cycles.
The predetermined number of times is larger for the central portion of the detection area where the presence of physical objects such as other vehicles outside the vehicle mounting the system (typically ahead of or behind the vehicle) during the operation of the vehicle is ordinarily stable than the predetermined number of times for the peripheral portions of the detection area where there is a possibility of frequent entry and exit of moving physical objects. Accordingly, the dropout of physical objects in the central portion of the detection area can be prevented, and the erroneous recognition of physical objects that are not present in the peripheral portions of the detection area can be reduced.